Operation of high speed, low/minimum wake passenger vessels on average water conditions presents many engineering challenges. When conventional V or inverted V type vessels are operated at high speeds many problems are encountered including, but not limited to, large destructive wake generation, tripping or excessive leaning and sliding in corners and inadequate propeller grip due to aeration cavitation and related steering problems as well as transverse, side to side load change stability and forward loading.
In an attempt to reduce or eliminate many of the above listed problems, such as, improve transverse stability, reduce wave impact or make specific design changes, prior art inventors have devised many means of addressing some of the preexisting problems. These prior art hull inventions, both V and inverted V hulls address, almost exclusively, monohulled craft. These monohull prior art vessels have hull beam to length ratios of no more then 4 to 1 and in most instances not over 3:1. There are several prior art inventors such as Gold Coast Yachts Patent number 5,191,848 dated 1993, that have designed a wave piercing SWATH type (small waterplane submerged primary hulls) catamarans that can produce reasonable speeds with reasonable wake. The draw backs associated with catamarans of the SWATH type and extremely long narrow hull catamarans (16:1 or greater ratio) is generally deep draft, low load bearing for the size of the vessel and higher potential of underwater hull damage. Other types of catamarans such as wave piercing hulls are directed toward passenger comfort without regard to the draft or wave generating problems presented by wake size restrictions in waterway systems most suitable to passenger ferry service.
The present invention, addresses and resolves the problems that all of the prior art vessel inventions have attempted to overcome in both monohull and multihull craft including inverted V bottom monohulled craft commonly referred to as the Hickman sea sleds of 1914 or air cushion vessels, such as the keelless concave hull of Charles English, Sr. 1996, Pat. No. 5,497,722 and trihedral step hull air entrapment vessels such as Stolk 1992 Pat. No. 5,140,930. One major problem with prior art planing hull designs both conventional monohulls with V bottoms and inverted V bottoms, is the problem of either sliding sideways in a hard turn due to the vessel leaning into a turn which results in a large flat bottom area becoming parallel to the water surface often times resulting in uncontrolled side sliding or, in the case of the inverted V hull the hull side away from the direction of turn stops the vertical side of hull from slipping sideways enough to allow the vessel to remain upright or lean into a turn. When this happens the vessel weight above the waterline continues to move away from the turn causing a tripping action that can cause the craft to turn over in a direction away from the turn direction. This proven tripping of an inverted V vessel can cause serious dangers to vessel and occupants. The present invention eliminates the above identified problems due to its twin multihull configuration that prevents sliding due to its vertical sides and deep chines as well as being virtually impervious to tripping due to the fact that not enough force above the waterline can be generated to physically lift the hull on the inside of the turn out of the water. The result is that the present invention turns quickly and safely without leaning, sliding or tripping.
Prior art hull forms have not specifically addressed the growing problem of large destructive wakes at speed with the result that many areas have been forced to mandate either no/minimum wake zones or even 5 mph no wake areas to protect both the environment and other water craft. The present invention has been developed, designed and model tested with the principal objective of generating little or minimum wake at speed even when heavily loaded. Heretofore V and modified V designs have specifically avoided the wake issue concentrating on softer riding, increased economy and certain handling characteristics. The inverted V hulls have in one or two instances referenced straight vertical sides but with chines inboard of the sides such as the Hickman Sea Sled which still generates some bow and side wake, or English, which identifies a straight side from the waterline down to the chine with the sides curving heavily outboard above the at rest waterline to the gunwale. When the vessel is in motion it can cause water to curl away from the vessel when the stern settles or the vessel "cuts down" into a wave, this outward thrown water can cause side wakes. A wide transom vessel, typical of all planing monohull vessels inherently cause a larger stern wake due to the sudden release of pressure at the transom which causes a large "hump" of water to rise up aft of the craft. This hump of water then mixes with the side hull wake and moves sideways as well as aft of the vessel often causing large destructive wakes to flow away to the sides. The remaining problem with inverted V hulls is that they become nearly flat at the aft end of the craft which allows the pressures generated under the hull at the forward end of the craft to force the water, both hard and aerated, to escape sideways under the aft area of the chines again causing side generated waves or wake.